The semiconductor industry is a highly competitive market. Accordingly, the ability for an IC fabricator to minimize waste and maximize the real estate usage of a substrate may give the IC fabricator a competitive edge. Substrate processing is usually a complex process that involves many parameters. The ability to produce quality devices may depend upon an IC fabricator's ability to have highly granular control of the different processing parameters. A common cause of defective devices is the lack of uniformity during substrate processing. A factor that may impact uniformity is the distribution of power to the processing environment.
To facilitate discussion, FIG. 1A shows a simple block diagram of a simple power arrangement 100 in which a single power source is connected to a single electrode, such as an RF (radio frequency) power supply that supplies RF power to an electrostatic chuck. Traditionally the power source is located at a distance from the plasma processing system. In order to send the power from an RF (radio frequency) generator 104 to a matching network 118, the power may be sent via a transmission line 116. Usually, transmission line 116 is a 50-ohm transmission line.
With reference to FIG. 1, incoming AC power from AC line 102 may be sent to RF generator 104. Within RF generator 104, an AC-DC converter 106 may convert the incoming AC power into direct current (DC) power. Once the AC power has been converted, the DC power may be transformed by a power amplifier 110. To modulate the converted DC power, power amplifier (PA) 110 may employ filtering (114) to remove spurious noise components such as high frequency harmonics. Inside RF generator 104 may also be a controller 108, which may be employed to control the different processes that may be occurring with RF generator 104 and to interface with external control.
Metrology probe 112 may be configured at the input or output end of the transmission line, which ma be 50-ohms (typical in IC manufacturing) or 75-ohms transmission link (typical in communication), to identify the amount of power being outputted, voltage, and/or current that may be outputted.
Matching network 118 may be employed to match the output impedance of the RF generator with the impedance of the processing environment within a processing chamber 120. Matching network 118 may be configured with a metrology probe to monitor the power, voltage, and/or current in order to perform the matching. Power is usually monitored for both a capacitive and inductive environment. However, voltage is typically monitored in a capacitive environment and current is monitored in an inductive environment.
From matching network 118, RF power is transferred to processing chamber 120. In the example of FIG. 15 processing chamber 120 is an asymmetric chamber, i.e., the ground electrode has a different effective area compare to the power electrode. However, chamber 120 may be a symmmetric chamber, if desired. Power may be distributed into processing chamber 120 via an upper electrode, such as a capacitive electrode 122. Processing chamber 120 and capacitive electrode 122 may form a parallel plate arrangement. Alternatively, power may be distributed into the processing chamber via a single inductive antenna 124, as shown by FIG. 1B.
Alternatively, FIG. 1C shows a simple block diagram of a simple capacitively-coupled power arrangement in which a single power source is balanced (e.g., push-pull configuration). FIG. 1D shows a similar balanced arrangement except the power arrangement is an inductive arrangement. In a balanced environment an equal area of a set of electrodes 130 (FIG. 1C) or a set of antenna 132 (FIG. 1D) has applied potential negatively and positively simultaneously. Thus, the net current to ground is zero. This arrangement may reduce problems that may be associated with ground return and may reduce sputtering that may occur in processing chamber 120.
In the power arrangements as described in FIGS. 1A, 1B, 1C, and 1D, the user has little or no control on how power may be distributed into the processing chamber except in a global fashion. In other words, the user is unable to direct different amounts of power into different regions of the processing chamber in order to control the uniformity of the plasma As a result, the configurations of the power arrangements as described in FIGS. 1A, 1B, 1C, and 1D provide the user with insufficient control over substrate processing uniformity. Also, as the chamber scales, the power arrangements, as described in the aforementioned figures, can be inefficient and/or expensive since the arrangements often require a large matching network to optimize power transfer.
To provide more control, a plurality of power arrangements as described above may be employed. However, the implementation of such an arrangement may become very expensive and complex.
FIG. 2A shows a simple diagram illustrating a multiple electrodes arrangement with a single power source. Similar to FIG. 1A, a power arrangement 200 may include an AC line 202 connected to an RF generator 204, which may include an AC-DC converter 206, a controller 208, a power amplifier 210, and a metrology probe 212. Power may be converted, modulated, and sent to a matching network 218 via a transmission line 216.
In a multiple electrode arrangement, matching network 218 tends to be a complex matching network in order to generate multiple outputs. To manage the matching network, controller 208 may also be employed, as shown by a match control path 230 between controller 208 and matching network 218. In this example, two outputs (V1 and V2) may be produced. An unbalanced circuit 266 may be established between matching network 218 and processing chamber 220, which may be grounded. The circuit may be unbalanced since the voltage output (V1) to capacitive plate 224 may be less (e.g., smaller in amplitude) than the voltage output (V2) to capacitive plate 222. To match the two voltage outputs, matching network 218 may be manipulated to alter the voltage outputs to capacitive plate 224 or to capacitive plate 222.
Alternatively, the RF power may be flowing through a pair of unbalanced inductive antenna (272 and 274), as shown in FIG. 2B. Similar to FIG. 1C, power arrangement 200 may also be implemented as a balanced push-pull arrangement in which a pair of capacitive plates (282 and 284 of FIG. 2C) or a pair of inductive antenna (292 and 294 of FIG. 2D) may be employed to create a circuit.
The power distribution arrangement of a single generator to multiple electrodes typically involves current steering (i.e., selecting whether more or less current should be at each electrode) to occur. In an example, in a balanced inductive arrangement (as that of FIG. 2D), current steering may occur between the pair of antenna to enable the current flowing across the substrate to be manipulated. However, steering the current in order to create a uniform processing environment may require a complex, bulky matching network be implemented.
In an example, in a balanced inductive environment (as shown in FIG. 2D), a complex and bulky) matching network may be required in order to accommodate a plurality of electrical components, such as transmission line straps (f1, f2, f3, and f4), to the set of antenna, for example. In order to maintain symmetry and ensure ground return, the electrical component may be shielded by an enclosure.
The aforementioned power arrangement as shown in FIGS. 2A-2D can become very complex, very complicated, and very expensive to build and maintain as the number of electrical components required to perform current steering increase. In order to determine the amount of power actually being outputted into each set of electrodes/antenna, additional components, such as metrology probes, may have to be included into the matching network, thereby causing the matching network to become even more complex/bulkier and more expensive. Because of this, the number of elements is often restricted to very few such as only one or two and consequently, highly granular control is not possible.